The present invention relates to a hold type display device, typically a TFT liquid crystal display, and more particularly to a display device with an improved quality of moving images.
An active matrix type display device such as a TFT liquid crystal display has characteristics of a thin type, high precision and a low power consumption, and is widely used for a mobile apparatus such as a mobile phone and a portable information terminal.
High performance is progressing in mobile apparatus, particularly in mobile phones, and scenes using moving images have increased such as one segment broadcasting, reproduction of recorded moving images and applications including games. TFT liquid crystal is driven by a hold type scheme by which the same image continues to be displayed during one frame period. Therefore, as moving images are displayed, pictures are left as after images in retinas, and there occurs a phenomenon (hereinafter called “moving image blur”) that the contours of displayed picturers look less clear and sharp.
U.S. Patent Publication 6473077 (JP-A-2000-122596) proposes a method of mitigating moving image blur to cancel retina after images by inserting a black display period in one frame, as a measure to prevent quality deterioration of a hold type display device. However, inserting this black display period is a pseudo impulse type driving method typically used in CRT's, and lowers the maximum luminance and contrast of displayed pictures.
U.S. Patent Unexamined Publication 20050253785 (JP-A-2005-173387) proposes a method of preventing a luminance and contrast from being lowered, by which one frame is divided into several subframes, and the luminance lowered by inserting a black display period is compensated by another subframe. Although this method is the pseudo impulse type driving method, the luminance and contrast can be prevented from being lowered as viewed in one frame period. With this method, it is necessary to generate low luminance subframe data for the pseudo impulse driving method and high luminance subframe data for the luminance compensation, from one frame data input to the system. This data conversion process uses a look-up table (hereinafter called “LUT”).
In order to realize this method, a storage device of a large capacity is necessary for LUT which stores data subjected to the conversion process. If this storage is mounted on hardware such as LSI, the circuit area increases resulting in an increase in cost. It is also difficult to apply this method to mobile apparatus having strict restrictions of the circuit area.